Transmission diversity and multiplexing for harq-ack signals in communication systems

ABSTRACT

A method and apparatus are described for a User Equipment (UE) to transmit in a control channel ACKnowledgement signals associated with a Hybrid Automatic Repeat reQuest process (HARQ-ACK signals) in response to receiving Transport Blocks (TBs) transmitted from a base station. The UE conveys the HARQ-ACK information by selecting one resource from multiple resources in the control channel and by selecting a constellation point of the modulation scheme for the HARQ-ACK signal. Transmission diversity is supported using different control channel resources that are already available to the UE without configuring additional resources. Design principles are described to optimally map the HARQ-ACK information to control channel resources and modulation constellation points for a Time Division Duplex (TDD) system and for a Frequency Division Duplex (FDD) system.

PRIORITY

This application is a Continuation Application of U.S. patentapplication Ser. No. 14/264,819, which was filed in the U.S. Patent andTrademark Office on Apr. 29, 2014, which is a continuation of U.S.patent application Ser. No. 12/907,606, which was filed in the U.S.Patent and Trademark Office on Oct. 19, 2010, and claims priority under35 U.S.C. §119(e) to Provisional Application Nos. 61/252,854, and61/355,871, entitled “Transmission Diversity and Multiplexing forHARQ-ACK Signals in TDD Communication Systems,” which were filed in theUnited States Patent and Trademark Office on Oct. 19, 2009, and Jun. 17,2010, respectively, the content of each of which is incorporated hereinby reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is directed generally to wireless communicationsystems, and more specifically, to transmission methods foracknowledgement signals including the application of transmissiondiversity.

2. Description of the Art

A communication system includes a DownLink (DL), supportingtransmissions of signals from a base station (Node B) to User Equipments(UEs), and an UpLink (UL), supporting transmissions of signals from UEsto the Node B. A UE, also commonly referred to as a terminal or a mobilestation, may be fixed or mobile and may be a wireless device, a cellularphone, a personal computer device, and the like. A Node B is generally afixed station and may also be referred to as a Base Transceiver System(BTS), an access point, or some other terminology.

The UL signals from a UE include data signals, carrying the informationcontent, control signals, and Reference Signals (RS), which are alsoknown as pilot signals. The UL control signals include acknowledgementsignals associated with the application of a Hybrid Automatic RepeatreQuest (HARQ) process and are in response to the correct or incorrect,respectively, reception of data Transport Blocks (TBs) by the UE. ULcontrol signals can be transmitted separately from data signals in aPhysical Uplink Control CHannel (PUCCH) or, they can be transmittedtogether with data signals, in a Physical Uplink Shared CHannel (PUSCH)over a Transmission Time Interval (TTI). The UE receives TBs from theNode B through a Physical Downlink Shared CHannel (PDSCH) and the Node Bschedules transmission of the TBs in the PDSCH or transmission of theTBs from the UE in the PUSCH through Downlink Control Information (DCI)formats transmitted in a Physical Downlink Control CHannel (PDCCH).

A PUCCH structure for the HARQ ACKnowledgement (HARQ-ACK) signaltransmission in the UL TTI, which, for simplicity, is assumed to includeone sub-frame, is illustrated in FIG. 1. The sub-frame 110 includes twoslots. Each slot 120 includes N_(symb) ^(UL) symbols for thetransmission of HARQ-ACK signals 130, or of RS 140 which enable coherentdemodulation of the HARQ-ACK signals. Each symbol further includes aCyclic Prefix (CP) to mitigate interference due to channel propagationeffects. The transmission in the first slot may be at a different partof the operating BandWidth (BW) than the second slot to providefrequency diversity. The operating BW is assumed to consist of frequencyresource units, which will be referred to as Resource Blocks (RBs). EachRB is further assumed to include N_(sc) ^(RB) sub-carriers, or ResourceElements (REs), and a UE transmits HARQ-ACK signals and RS over one RB150.

A structure for the HARQ-ACK signal transmission in one slot of thePUCCH is illustrated in FIG. 2. The transmission in the other slot isassumed to effectively have the same structure. The HARQ-ACK bits b 210modulate 220 a “Constant Amplitude Zero Auto-Correlation (CAZAC)”sequence 230, using, for example, Binary Phase Shift Keying (BPSK) orQuaternary Phase Shift Keying (QPSK) modulation, which is thentransmitted after performing an Inverse Fast Frequency Transform (IFFT)as it is next described. The RS 240 is transmitted through thenon-modulated CAZAC sequence.

An example of CAZAC sequences is given by Equation (1).

$\begin{matrix}{{c_{k}(n)} = {\exp \left\lbrack {\frac{{j2\pi}\; k}{L}\left( {n + {n\frac{n + 1}{2}}} \right)} \right\rbrack}} & (1)\end{matrix}$

In Equation (1), L is the length of the CAZAC sequence, n is the indexof an element of the sequence n={0, 1, . . . , L−1}, and k is the indexof the sequence. If L is a prime number, there are L−1 distinctsequences which are defined as k ranges in {0, 1, . . . , L−1}. If an RBis comprised of an even number of REs, such as, for example, N_(sc)^(RB)=12, CAZAC sequences with an even length can be directly generatedthrough a computer search for sequences satisfying the CAZAC properties.

FIG. 3 illustrates a UE transmitter structure for the HARQ-ACK signal inthe PUCCH. The frequency-domain version of a computer generated CAZACsequence 310 is assumed. The first RB and second RB are selected 320 fortransmission 330 of the CAZAC sequence in the first and second slots,respectively, an IFFT is performed 340, and a Cyclic Shift (CS), as itis subsequently described, applies to the output 350. Finally, the CP360 and filtering 370 are applied to the transmitted signal 380. A UE isassumed to apply zero padding in REs that are not used for its signaltransmission and in guard REs (not shown). Moreover, for brevity,additional transmitter circuitry such as a digital-to-analog converter,analog filters, amplifiers, and transmitter antennas as they are knownin the art, are not shown.

The reverse (complementary) transmitter functions are performed by theNode B for the HARQ-ACK signal reception in the PUCCH. This isillustrated in FIG. 4, where the reverse operations of those in FIG. 3apply. An antenna receives the RF analog signal and after furtherprocessing units (such as filters, amplifiers, frequencydown-converters, and analog-to-digital converters) the received digitalsignal 410 is filtered 420 and the CP is removed 430. Subsequently, theCS is restored 440, a Fast Fourier Transform (FFT) 450 is applied, thefirst RB and the second RB of the signal transmission 460 in the firstslot and in the second slot, respectively, are selected 465, and thesignal is correlated 470 with the replica 480 of the CAZAC sequence. Theoutput 490 can then be passed to a channel estimation unit, such as atime-frequency interpolator, in the case of RS, or to detect thetransmitted HARQ-ACK information.

Different CSs of the same CAZAC sequence provide orthogonal CAZACsequences and can be assigned to different UEs for orthogonalmultiplexing of signal transmissions in the same PUCCH RB. Thisprinciple is illustrated in FIG. 5. In order for the multiple CAZACsequences 510, 530, 550, 570 generated respectively from the multipleCSs 520, 540, 560, 580 of the same root CAZAC sequence to be orthogonal,the CS value □ 590 should exceed the channel propagation delay spread D(including time uncertainty errors and filter spillover effects). If Tsis the symbol duration, the number of such CSs is equal to themathematical floor, i.e., rounding down, of the ratio T_(S)/D.

In addition to orthogonal multiplexing of HARQ-ACK signal transmissionsfrom different UEs in the same RB using different CS of a CAZACsequence, orthogonal multiplexing can also be achieved in the timedomain using Orthogonal Covering Codes (OCCs). For example, in FIG. 2,the HARQ-ACK signal can be modulated by a length-4 OCC, such as aWalsh-Hadamard (WH) OCC, while the RS can be modulated by a length-3OCC, such as a DFT OCC (not shown for brevity). In this manner, thePUCCH multiplexing capacity is increased by a factor of 3 (determined bythe OCC with the smaller length). The sets of WH OCCs, {W₀, W₁, W₂, W₃},and DFT OCCs, {D₀, D₁, D₂}, are:

${\begin{bmatrix}W_{0} \\W_{1} \\W_{2} \\W_{3}\end{bmatrix} = \begin{bmatrix}1 & 1 & 1 & 1 \\1 & {- 1} & 1 & {- 1} \\1 & 1 & {- 1} & {- 1} \\1 & {- 1} & {- 1} & 1\end{bmatrix}},{\begin{bmatrix}D_{0} \\D_{1} \\D_{2}\end{bmatrix} = {\begin{bmatrix}1 & 1 & 1 \\1 & ^{{- {j2\pi}}/3} & ^{{- {j4\pi}}/3} \\1 & ^{{- {j4\pi}}/3} & ^{{- {j2\pi}}/3}\end{bmatrix}.}}$

Table 1 illustrates a mapping for a PUCCH resource n_(PUCCH), used forHARQ-ACK signal transmission, to an OCC n_(oc) and a CS α assuming atotal of 12 CS of the CAZAC sequence per PUCCH symbol.

TABLE 1 HARQ-ACK Resource Mapping to OC and CS OC n_(oc) for HARQ-ACKand for RS CS α W₀, D₀ W₁, D₁ W₃, D₂ 0 n_(PUCCH) = 0 n_(PUCCH) = 12 1n_(PUCCH) = 6 2 n_(PUCCH) = 1 n_(PUCCH) = 13 3 n_(PUCCH) = 7 4 n_(PUCCH)= 2 n_(PUCCH) = 14 5 n_(PUCCH) = 8 6 n_(PUCCH) = 3 n_(PUCCH) = 15 7n_(PUCCH) = 9 8 n_(PUCCH) = 4 n_(PUCCH) = 16 9 n_(PUCCH) = 10 10n_(PUCCH) = 5 n_(PUCCH) = 17 11 n_(PUCCH) = 11

The DCI formats are transmitted in elementary units, which are referredto as Control Channel Elements (CCEs). Each CCE consists of a number ofREs and the UEs are informed of the total number of CCEs, N_(CCE),through the transmission of a Physical Control Format Indicator CHannel(PCFICH) by the Node B. For a Frequency Division Duplex (FDD) system andPDSCH transmission scheduled by a DCI format, the UE determinesn_(PUCCH) from the first CCE, n_(CCE), of the DCI format with theaddition of an offset N_(PUCCH) that is configured by higher layers(such as the Radio Resource Control (RRC) layer) andn_(PUCCH)=n_(CCE)+N_(PUCCH). For a Time Division Duplex (TDD) system,the determination of n_(PUCCH) is more complex, as further discussedbelow, but the same mapping principle using the CCEs of the DCI formatscheduling the corresponding PDSCH transmission applies.

In TDD systems, DL and UL transmissions occur in different sub-frames.For example, in a frame including 10 sub-frames, some sub-frames may beused for DL transmissions and some sub-frames may be used for ULtransmissions.

FIG. 6 illustrates a 10 millisecond (ms) frame structure which includestwo identical half-frames. Each 5 ms half-frame 610 is divided into 8slots 620 and 3 special fields: a DL ParT Symbol (DwPTS) 630, a GuardPeriod (GP) 640, and an UL ParT Symbol (UpPTS) 650. The length ofDwPTS+GP+UpPTS is one sub-frame (1 ms) 660. The DwPTS may be used forthe transmission of synchronization signals from the Node B while theUpPTS may be used for the transmission of random access signals fromUEs. The GP facilitates the transition between DL and UL transmissionsby absorbing transient interference.

In TDD systems, the number of DL and UL sub-frames per frame can bedifferent and multiple DL sub-frames may be associated with a single ULsub-frame. The association between the multiple DL sub-frames and thesingle UL sub-frame is that HARQ-ACK information generated in responseto PDSCH transmissions in the multiple DL sub-frames needs to beconveyed in the single UL sub-frame.

A first method for a UE to convey HARQ-ACK information in a single ULsub-frame, in response to PDSCH transmissions in multiple DL sub-frames,is HARQ-ACK bundling where the UE sends a positive ACKnowledgement (ACK)only if all TBs in the respective PDSCHs are received correctly andsends a Negative ACKnowledgement (NACK) in other cases. Therefore,HARQ-ACK bundling results in unnecessary retransmissions and reduced DLthroughput as a NACK is sent even when the UE correctly receives some,but not all, TBs in the respective PDSCHs. Another method for a UE toconvey HARQ-ACK information in a single UL sub-frame, in response to TBsin the respective PDSCHs in multiple DL sub-frames, is HARQ-ACKmultiplexing, which is based on PUCCH resource selection for theHARQ-ACK signal transmission as it is subsequently described. Theinvention primarily focuses on HARQ-ACK multiplexing.

In one embodiment, there could be 1, 2, 3, 4 or 9 DL sub-framesassociated with 1 UL sub-frame. Therefore, assuming that a UE receives amaximum of 2 TBs per PDSCH in a DL sub-frame, the number of HARQ-ACKbits to be transmitted in the UL sub-frame can be 1, 2, 3, 4, 6, 8, 9 or18. Supporting such a dynamic range of number of HARQ-ACK bits istypically not desirable as it is difficult to ensure, at the Node B, therequired detection reliability, including the absence of an expectedHARQ-ACK signal transmission due to a missed DCI format for PDSCHtransmission to the UE (referred to as DTX). To reduce the number ofHARQ-ACK bits, bundling can be applied in the spatial domain, resultingin a single HARQ-ACK bit in the case of 2 TBs in a PDSCH. This reducesthe number of possible HARQ-ACK bits in the UL sub-frame to 1, 2, 3, 4,or 9. Further bundling in the time domain can be applied to the case of9 HARQ-ACK bits so that the maximum number is always reduced to 4HARQ-ACK bits. HARQ-ACK multiplexing can then be used to transmit up to4 HARQ-ACK bits.

With HARQ-ACK multiplexing, a UE conveys a HARQ-ACK value (ACK, NACK, orDTX) for each of the multiple DL sub-frames even if PDSCH transmissionto that UE did not occur in all DL sub-frames. For example, if there are4 DL sub-frames for which HARQ-ACK information needs to be transmittedin the same UL sub-frame, then, with HARQ-ACK multiplexing, the HARQ-ACKsignal from a UE conveys HARQ-ACK information for each of the 4 DLsub-frames even if the PDSCH transmission to the UE occurs in less than4 DL sub-frames.

Table 2 illustrates the HARQ-ACK multiplexing in the case in which theUE conveys HARQ-ACK information for 2 DL sub-frames in the same ULsub-frame (a HARQ-ACK state consists of 2 HARQ-ACK values). The UEselects one PUCCH resource, n_(PUCCH)(0) or n_(PUCCH)(1), and one QPSKconstellation point (on a constellation diagram) for the transmission ofthe QPSK modulated HARQ-ACK signal depending on the HARQ-ACKinformation. Each PUCCH resource is determined from the first CCE of theDCI format for the respective PDSCH transmission in each of the 2 DLsub-frames.

TABLE 2 HARQ-ACK Multiplexing for 2 DL Sub-Frames HARQ-ACK(0), HARQ-ACK(1) n_(PUCCH) QPSK ACK, ACK n_(PUCCH) (1) 1, 1 ACK, NACK/DTXn_(PUCCH) (0) 0, 1 NACK/DTX, ACK n_(PUCCH) (1) 0, 0 NACK/DTX, NACKn_(PUCCH) (1) 1, 0 NACK, DTX n_(PUCCH) (0) 1, 0 DTX, DTX N/A N/A

FIG. 7 illustrates the HARQ-ACK signal transmission process in Table 2.If no DCI format is received by the UE, there is no HARQ-ACK signaltransmission. If the UE receives a DCI format in the second DL sub-frame702, it uses the respective first CCE to determine n_(PUCCH)(1) 710 forthe HARQ-ACK signal transmission having {NACK/DTX, ACK} 722, {ACK, ACK}724, and {NACK/DTX, NACK} 726 as the possible HARQ-ACK states which arethen mapped to QPSK constellation points. If the UE receives a DCIformat only in the first DL sub-frame 704, it uses the respective firstCCE to determine n_(PUCCH)(0) 730 for the HARQ-ACK signal transmissionhaving {ACK, NACK/DTX} 742, and {NACK, DTX} 744 as the possible HARQ-ACKstates which are then mapped to QPSK constellation points.

Table 2 illustrates the HARQ-ACK multiplexing in the case in which theUE conveys HARQ-ACK information for 2 DL sub-frames in the same ULsub-frame (a HARQ-ACK state consists of 2 HARQ-ACK values). The UEselects one PUCCH resource, n_(PUCCH)(0) or n_(PUCCH)(1), and one QPSKconstellation point for the transmission of the QPSK modulated HARQ-ACKsignal depending on the HARQ-ACK information. Each PUCCH resource isdetermined from the first CCE of the DCI format for the respective PDSCHtransmission in each of the 2 DL sub-frames.

Table 3 illustrates the HARQ-ACK multiplexing in the case in which theUE conveys HARQ-ACK information for 3 DL sub-frames in the same ULsub-frame (a HARQ-ACK state consists of 3 HARQ-ACK values). The UEselects one PUCCH resource, n_(PUCCH)(0), or n_(PUCCH)(1), orn_(PUCCH)(2) and one QPSK constellation point for the transmission ofthe QPSK modulated HARQ-ACK signal, depending on the HARQ-ACKinformation. Each PUCCH resource is determined from the first CCE of theDCI format for the respective PDSCH transmission in each of the 3 DLsub-frames. Explicit DTX indication is possible through the inclusion inthe DCI formats for PDSCH transmission of a Downlink Assignment Index(DAI) Information Element (IE) indicating the cumulative number ofassigned PDSCH transmission(s) to the UE.

TABLE 3 HARQ-ACK Multiplexing for 3 DL Sub-Frames Entry HARQ-ACK(0),HARQ-ACK(1), HARQ- Number ACK(2) n_(PUCCH) QPSK  1 ACK, ACK, ACKn_(PUCCH) (2) 1, 1  2 ACK, ACK, NACK/DTX n_(PUCCH) (1) 1, 1  3 ACK,NACK/DTX, ACK n_(PUCCH) (0) 1, 1  4 ACK, NACK/DTX, NACK/DTX n_(PUCCH)(0) 0, 1  5 NACK/DTX, ACK, ACK n_(PUCCH) (2) 1, 0  6 NACK/DTX, ACK,NACK/DTX n_(PUCCH) (1) 0, 0  7 NACK/DTX, NACK/DTX, ACK n_(PUCCH) (2) 0,0  8 DTX, DTX, NACK n_(PUCCH) (2) 0, 1  9 DTX, NACK, NACK/DTX n_(PUCCH)(1) 1, 0 10 NACK, NACK/DTX, NACK/DTX n_(PUCCH) (0) 1, 0 11 DTX, DTX, DTXN/A N/A

Finally, Table 4 describes the HARQ-ACK multiplexing in case the UEconveys HARQ-ACK information for 4 DL sub-frames in the same ULsub-frame (a HARQ-ACK state consists of 3 HARQ-ACK values). The UEselects one PUCCH resource, n_(PUCCH)(0) , or n_(PUCCH)(1) n_(PUCCH)(2),or n_(PUCCH)(3), and one QPSK constellation point for the transmissionof the QPSK modulated HARQ-ACK signal depending on the HARQ-ACKinformation. Each PUCCH resource is determined from the first CCE of theDCI format for the respective PDSCH transmission in each of the 4 DLsub-frames.

TABLE 4 HARQ-ACK Multiplexing for 4 DL Sub-Frames Entry HARQ-ACK(0),HARQ-ACK(1), Number HARQ-ACK(2), HARQ-ACK(3) n_(PUCCH) QPSK  1 ACK, ACK,ACK, ACK n_(PUCCH) (1) 1, 1  2 ACK, ACK, ACK, NACK/DTX n_(PUCCH) (1) 1,0  3 NACK/DTX, NACK/DTX, NACK, DTX n_(PUCCH) (2) 1, 1  4 ACK, ACK,NACK/DTX, ACK n_(PUCCH) (1) 1, 0  5 NACK, DTX, DTX, DTX n_(PUCCH) (0) 1,0  6 ACK, ACK, NACK/DTX, NACK/DTX n_(PUCCH) (1) 1, 0  7 ACK, NACK/DTX,ACK, ACK n_(PUCCH) (3) 0, 1  8 NACK/DTX, NACK/DTX, NACK/DTX, n_(PUCCH)(3) 1, 1   NACK  9 ACK, NACK/DTX, ACK, NACK/DTX n_(PUCCH) (2) 0, 1 10ACK, NACK/DTX, NACK/DTX, ACK n_(PUCCH) (0) 0, 1 11 ACK, NACK/DTX,NACK/DTX, NACK/DTX n_(PUCCH) (0) 1, 1 12 NACK/DTX, ACK, ACK, ACKn_(PUCCH) (3) 0, 1 13 NACK/DTX, NACK, DTX, DTX n_(PUCCH) (1) 0, 0 14NACK/DTX, ACK, ACK, NACK/DTX n_(PUCCH) (2) 1, 0 15 NACK/DTX, ACK,NACK/DTX, ACK n_(PUCCH) (3) 1, 0 16 NACK/DTX, ACK, NACK/DTX, NACK/DTXn_(PUCCH) (1) 0, 1 17 NACK/DTX, NACK/DTX, ACK, ACK n_(PUCCH) (3) 0, 1 18NACK/DTX, NACK/DTX, ACK, NACK/DTX n_(PUCCH) (2) 0, 0 19 NACK/DTX,NACK/DTX, NACK/DTX, ACK n_(PUCCH) (3) 0, 0 20 DTX, DTX, DTX, DTX N/A N/A

The main drawback of the mapping in Table 4 is that several HARQ-ACKstates are mapped to the same PUCCH resource and QPSK constellationpoint (i.e., they are overlapping). For example, 3 different HARQ-ACKstates in Table 4 (entries 2, 4, and 6) are mapped to PUCCH resourcen_(PUCCH)(1) and QSPK constellation point {1, 0}. Similarly, 3 otherHARQ-ACK states (entries 7, 12, and 17) are mapped to PUCCH resourcen_(PUCCH)(3) and QSPK constellation point {0, 1}. This overlap isunavoidable since the 20 HARQ-ACK states in Table 4 must be mapped to amaximum of 16 positions corresponding to 4 PUCCH resources and 4 QPSKconstellation points.

A consequence of the overlapping HARQ-ACK states in Table 4 is loss ofsystem throughput, as the Node B typically needs to assume thatnon-unique values correspond to NACK or DTX and perform HARQretransmissions although the UE may have actually correctly received theTBs of the respective PDSCHs. If the Node B schedules PDSCHtransmissions to a UE in the first and second sub-frames, it isgenerally unable to schedule PDSCH transmissions to the UE in the thirdor fourth sub-frames (entries 2, 4, and 6). Similarly, if the Node Bschedules PDSCH transmissions to a UE in the third and fourthsub-frames, it is generally unable to schedule PDSCH transmissions tothe UE in the first or second sub-frame (entries 7, 12, and 17).Therefore, the mapping in Table 4 should be improved to minimize oravoid the overlapping of HARQ-ACK states. Specific rules should also bedefined for iteratively constructing mapping Tables as the number ofHARQ-ACK states increases.

For a UE equipped with more than one transmitter antenna, TransmitterDiversity (TxD) can enhance the reliability of the received signal atthe Node B by providing spatial diversity. For HARQ-ACK signaltransmission, because of the OCC applied across PUCCH symbols andbecause of possible CS hopping across PUCCH symbols within a slot, theapplication of TxD methods using space-time coding is problematic.Conversely, Orthogonal Resource Transmission Diversity (ORTD), whereeach UE transmitter antenna uses a separate (orthogonal) PUCCH resource,can directly apply.

FIG. 8 illustrates the application of ORTD. The first UE transmitterantenna uses a first PUCCH resource 810, associated with the first CCEused to transmit the DCI format, and the second UE transmitter antennauses a second PUCCH resource 820, which can be assumed to be associatedwith a second CCE used to transmit the DCI format. Both antennastransmit the same information, which is either an ACK 830 and 850, or aNACK 840 and 860.

Although ORTD requires additional PUCCH resources, a UE may often haveavailable more than one orthogonal PUCCH resource for HARQ-ACK signaltransmission. For example, when the DCI format scheduling the PDSCHtransmission uses more than one CCE for its transmission, each CCEprovides an orthogonal PUCCH resource for HARQ-ACK signal transmission.However, without additional mechanisms, such as a separate configurationof an additional orthogonal PUCCH resource for UEs applying ORTD, theuse of ORTD for HARQ-ACK signal transmission is generally problematic asthe DCI format scheduling the respective PDSCH transmission may consistof only one CCE and the next CCE may be the first CCE used for thetransmission of another DCI format scheduling PDSCH transmission toanother UE.

The HARQ-ACK multiplexing used for TDD systems can be extended for FDDsystems using Carrier Aggregation (CA) where a UE receives multiplePDSCH transmissions in multiple DL cells in the same TTI. CA isfundamentally the parallelization of single-cell operation to multi-celloperation. For each PDSCH reception, the UE needs to convey to the NodeB one HARQ-ACK value (ACK, NACK, or DTX) in case the PDSCH conveyed oneTB and two HARQ-ACK values ({ACK, ACK}, {ACK, NACK}, {NACK, ACK}, {NACK,NACK} or DTX) in case the PDSCH conveyed two TBs.

Therefore, there is a need to enable ORTD for HARQ-ACK signaltransmission with multiplexing by utilizing available CCEs used fortransmission of respective DCI formats.

There is another need to optimize the use of PUCCH resources forHARQ-ACK signal transmission using multiplexing.

There is another need to minimize or avoid overlapping of HARQ-ACKstates onto the same PUCCH resources or QPSK constellation points and todefine iterative mapping rules as the number of HARQ-ACK statesincreases.

Finally, there is another need to support HARQ-ACK multiplexing for FDDsystems using carrier aggregation.

SUMMARY OF THE INVENTION

Accordingly, the present invention has been designed to solve at leastthe aforementioned limitations and problems in the prior art and toprovide the following advantages. An aspect of the present invention isto provide methods and an apparatus for a UE, operating either in a TDDsystem or in an FDD system with CA, to transmit to a base station aHARQ-ACK signal using ORTD where the HARQ-ACK signal is transmitted froma first UE antenna using a first resource associated with the receptionof a first TB and transmitted from a second UE antenna using a secondresource associated with the reception of a second TB.

In accordance with another aspect of the present invention, a method isprovided for a UE to transmit to a base station a HARQ-ACK signal usingresource multiplexing where, for the same size of HARQ-ACK information,a first mapping is used when the UE operates in a TDD system and asecond mapping is used when the UE operates in an FDD system and wherethe first mapping includes overlapping of different HARQ-ACK states ontothe same resource and the second mapping always associates differentHARQ-ACK states with different resources. In either mapping, if the lastvalue of the HARQ-ACK information is an ACK, the control resourcecorresponding to the DCI format used for scheduling the last receivedPDSCH is selected for the HARQ-ACK signal transmission.

In accordance with another aspect of the present invention, a method andapparatus are provided for a UE to transmit to a base station a HARQ-ACKsignal using resource multiplexing where the UE utilizes a first controlchannel resource when it receives one TB and it utilizes a first and asecond control channel resource when it receives two TBs where the UEpredicts the second control channel resource from the first controlchannel resource.

In accordance with another aspect of the present invention, a method isprovided for a User Equipment (UE) to transmit to a base station anacknowledgement signal, wherein the acknowledgement signal conveysacknowledgement information about the reception by the UE of a numberTransport Blocks (TBs) received by the UE over multiple transmissiontime intervals and is transmitted by selecting one resource frommultiple resources of a control channel and one constellation point frommultiple constellation points of a modulation scheme, the methodcomprises transmitting the acknowledgement signal to provideacknowledgement information which contains explicit indication of missedreception of a TB when the acknowledgment information consists of 2 or 3bits, and transmitting the acknowledgement signal to provideacknowledgement information which does not contain explicit indicationof missed reception of a TB when the acknowledgment information consistsof 4 bits.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of the presentinvention will be more apparent from the following detailed descriptiontaken in conjunction with the accompanying drawings, in which:

FIG. 1 is a diagram illustrating a PUCCH sub-frame structure forHARQ-ACK signal transmission;

FIG. 2 is a diagram illustrating a HARQ-ACK signal transmission in oneslot of the PUCCH sub-frame;

FIG. 3 is a block diagram illustrating a UE transmitter structure forthe HARQ-ACK signal in the PUCCH;

FIG. 4 is a block diagram illustrating a Node B receiver structure forthe HARQ-ACK signal in the PUCCH;

FIG. 5 is a diagram illustrating the use of different CSs of the sameCAZAC sequence provide orthogonal CAZAC sequences;

FIG. 6 is a diagram illustrating a 10 ms frame structure which consistsof two identical half-frames;

FIG. 7 is a diagram illustrating the HARQ-ACK signal transmission usingHARQ-ACK multiplexing in response to PDSCH reception in two DLsub-frames of a TDD system;

FIG. 8 is a diagram illustrating the application of ORTD;

FIG. 9 is a diagram illustrating the HARQ-ACK signal transmission withmultiplexing using ORTD;

FIG. 10 is a diagram illustrating the processing steps of the Node Breceiver's reception of a HARQ-ACK signal using multiplexing with ORTD;

FIG. 11 is a diagram illustrating the application of ORTD in case theDCI format scheduling PDSCH transmission in the last DL sub-frame can beassumed to be transmitted using 2 CCEs; and

FIG. 12 is a diagram illustrating the UE operation for HARQ-ACK signaltransmission with multiplexing in an FDD system where the UE receivesPDSCH in two DL cells.

DETAILED DESCRIPTION OF THE EMBODIMENTS OF THE PRESENT INVENTION

Various embodiments of the present invention will now be described morefully with reference to the accompanying drawings. This invention may,however, be embodied in many different forms and should not be construedas limited to the embodiments set forth herein. Rather, theseembodiments are provided so that this disclosure will be thorough,complete and will fully convey the scope of the invention to thoseskilled in the art.

Additionally, although the present invention is described in relation toa Single-Carrier Frequency Division Multiple Access (SC-FDMA)communication system, it also applies to all Frequency DivisionMultiplexing (FDM) systems in general and to an Orthogonal FrequencyDivision Multiple Access (OFDMA), OFDM, FDMA, Discrete Fourier Transform(DFT)-spread OFDM, DFT-spread OFDMA, SC-OFDMA, and SC-OFDM inparticular.

An embodiment of the present invention considers the application of ORTDfor the HARQ-ACK signal transmission when the DCI formats scheduling therespective PDSCH transmissions cannot be assumed to have beentransmitted using more than one CCE. Although the embodiment assumesHARQ-ACK multiplexing, the same principles apply in the case of HARQ-ACKbundling. Two UE transmitter antennas are assumed. In the case of morethan 2 UE transmitter antennas, virtualization to 2 UE transmitterantennas can be used. The embodiment further considers the case of M=2DL sub-frames (TDD system), for which the associated HARQ-ACK signaltransmissions are in the same UL sub-frame but the same principles applyfor an FDD system with CA over M=2 DL cells. The PUCCH resource forHARQ-ACK signal transmission corresponding to the first CCE used totransmit DCI format j, with j=0, . . . , M−1 is denoted as n_(PUCCH)(j).

FIG. 9 illustrates an embodiment for HARQ-ACK signal transmission withmultiplexing using ORTD. If the UE receives a DCI format in a second DLsub-frame 902, it uses the corresponding first CCE to determinen_(PUCCH)(1) 910 for the HARQ-ACK signal transmission from the firstantenna having {NACK/DTX, ACK} 922, {ACK, ACK} 924, and {NACK/DTX, NACK}926 as the possible HARQ-ACK states in the QPSK constellation. If the UEalso receives a DCI format in a first DL sub-frame 930, it uses thecorresponding first CCE to determine n_(PUCCH)(0) 940 for the HARQ-ACKsignal transmission from the second antenna having {NACK/DTX, ACK} 952,{ACK, ACK} 954, and {NACK/DTX, NACK} 956 as the possible HARQ-ACK statesin the QPSK constellation. If the UE receives a DCI format only in thefirst DL sub-fame 904, it uses the corresponding first CCE to determinethe n_(PUCCH)(0) 960 for the HARQ-ACK signal transmission having {ACK,NACK/DTX} 972, and {NACK, DTX} 974 as the possible HARQ-ACK states inthe QPSK constellation by either using 1 UE transmitter antenna or bycombining the transmission from multiple UE antennas (using precoding,for example).

Therefore, CCEs corresponding to multiple DCI formats, in respectivelymultiple DL sub-frames in a TDD system, or multiple DL cells in an FDDsystem, are used to support ORTD if the DCI format associated with thePUCCH resource for conventional HARQ-ACK signal transmission cannot beassumed to have been transmitted with more than one CCE.

A process for the Node B receiver to determine the PUCCH resources usedby the UE for the HARQ-ACK signal transmission with ORTD is to performenergy detection at the candidate PUCCH resources. Once the Node Bdetermines PUCCH resources with HARQ-ACK signal transmission, it canthen process the received signal according to the constellation pointsin FIG. 9. In the case of 2 UE transmitter antennas, the respectivesignals can be combined according to a known method, such asMaximal-Ratio Combining (MRC).

FIG. 10 illustrates the Node B receiver processing steps for thereception of a HARQ-ACK signal using multiplexing with ORTD. The Node Breceiver first examines 1010 whether the received signal energy inn_(PUCCH)(1) is above “Threshold 0.” If it is 1012, the Node B receiveralso examines 1020 whether the signal energy in n_(PUCCH)(0) is above“Threshold 1.” If it is 1022, the Node B receiver assumes the existenceof HARQ-ACK signals in n_(PUCCH)(0) and n_(PUCCH)(1) due to ORTD,proceeds with demodulating the HARQ-ACK signals transmitted from the 2UE antennas, and combines the outputs according to some method such asMRC 1030. If it is not 1024, the Node B receiver assumes the existenceof a HARQ-ACK signal only in n_(PUCCH)(1) and proceeds with itsdemodulation 1040. If the received signal energy in n_(PUCCH)(1) is notabove “Threshold 0” 1014, the Node B receiver examines whether thesignal energy in n_(PUCCH)(0) is above “Threshold 2” 1050. This step maybe the same as the one in step 1030, possibly with different values for“Threshold 1” and “Threshold 2.” If it is 1052, the Node B receiverdemodulates the HARQ-ACK signal and makes a decision for thecorresponding values 1060. If it is not 1054, the Node B may not performany further action and may assume that the UE did not correctly receiveany DCI format in the M=2 DL sub-frames 1070. It is observed that noadditional steps are required by the Node B receiver to support ORTDwith this method as the capability to compute the received signal energyin n_(PUCCH)(0) and n_(PUCCH)(1) and compare it to the respectivethresholds is already required to support HARQ-ACK multiplexing usingPUCCH resource selection.

Although the embodiment in FIG. 9 considers that ORTD may not apply ifthe UE receives a DCI format only in the first DL sub-frame, analternative embodiment is to allow for ORTD to apply if the UE receivesa DCI format only in the first DL sub-frame by allowing the UE to assumethat the DCI format in the first DL sub-frame includes at least 2 CCEs.No such requirement is needed for the DCI formats transmitted to the UEin the remaining DL sub-frames for which the HARQ-ACK signaltransmission is in the same UL sub-frame, and ORTD can apply asdescribed in conjunction with FIG. 9.

Another embodiment of the present invention considers iterative mappingrules, as the number of DL sub-frames (TDD system) for which theHARQ-ACK signal transmissions need to be in the same UL sub-frameincreases, in order to minimize the number of overlapping HARQ-ACKstates. The iterative mapping rules for the HARQ-ACK statescorresponding to M DL sub-frames having the HARQ-ACK signal transmissionin the same UL sub-frame are:

A HARQ-ACK state with M values (for M DL sub-frames) having arbitraryM−1 first values and NACK/DTX or DTX as its last (M-th) value is mappedto the same PUCCH resource and QPSK constellation point as the HARQ-ACKstate with the same M−1 values (for M−1 DL sub-frames).

The HARQ-ACK state with MACK values is mapped to n_(PUCCH)(M−1) andalways to the same QPSK constellation point.

If all first M−1 HARQ-ACK values include DTX, the M-th HARQ-ACK value ismapped to n_(PUCCH)(M−1) if it is an ACK. The same may apply in the caseof a NACK.

If all first M−1 HARQ-ACK values include DTX and the M-th HARQ-ACK valueis a NACK, the HARQ-ACK state may be mapped to the same n_(PUCCH)(M−k),1<k≦M and QPSK constellation point as a HARQ-ACK state with M−1 valueswhere all M−1 values are combinations of DTX and NACK (for example,entry 8 in Table 7). This provides an additional n_(PUCCH)(M−1) resourcefor mapping a HARQ-ACK state having ACK as its last value.

The remaining HARQ-ACK states, which always have an ACK value as theirlast value, are either mapped on a n_(PUCCH)(M−k), 1<k≦M, if anyrespective QPSK constellation points are available (Table 6), or theyare mapped on n_(PUCCH)(M−1) with priority to available QPSKconstellation points (Table 7). Because there are more remainingHARQ-ACK states than available resources, some HARQ-ACK states areinevitably mapped to the same resource. The objective in this case is tominimize the number of unnecessary retransmissions. All HARQ-ACK stateswith M values having an ACK value as the last value may be mapped onn_(PUCCH)(M−1) (Table 8).

TABLE 6 HARQ-ACK Multiplexing for 4 Node B PDSCH Transmissions EntryHARQ-ACK(0), HARQ-ACK(1), Number HARQ-ACK(2), HARQ-ACK(3) n_(PUCCH) QPSK 1 ACK, ACK, ACK, ACK n_(PUCCH) (3) 1, 1  2 ACK, ACK, ACK, NACK/DTXn_(PUCCH) (2) 1, 1  3 NACK/DTX, NACK/DTX, NACK, DTX n_(PUCCH) (2) 0, 1 4 ACK, ACK, NACK/DTX, ACK n_(PUCCH) (1) 0, 1  5 NACK, DTX, DTX, DTXn_(PUCCH) (0) 1, 0  6 ACK, ACK, NACK/DTX, NACK/DTX n_(PUCCH) (1) 1, 1  7ACK, NACK/DTX, ACK, ACK n_(PUCCH) (3) 0, 1  8 NACK/DTX, NACK/DTX,n_(PUCCH) (3) 0, 0 NACK/DTX, NACK  9 ACK, NACK/DTX, ACK, NACK/DTXn_(PUCCH) (0) 1, 1 10 ACK, NACK/DTX, NACK/DTX, ACK n_(PUCCH) (0) 0, 0 11ACK, NACK/DTX, NACK/DTX, NACK/DTX n_(PUCCH) (0) 0, 1 12 NACK/DTX, ACK,ACK, ACK n_(PUCCH) (3) 0, 1 13 NACK/DTX, NACK, DTX, DTX n_(PUCCH) (1) 1,0 14 NACK/DTX, ACK, ACK, NACK/DTX n_(PUCCH) (2) 1, 0 15 NACK/DTX, ACK,NACK/DTX, ACK n_(PUCCH) (1) 0, 1 16 NACK/DTX, ACK, NACK/DTX, NACK/DTXn_(PUCCH) (1) 0, 0 17 NACK/DTX, NACK/DTX, ACK, ACK n_(PUCCH) (3) 0, 1 18NACK/DTX, NACK/DTX, ACK, NACK/DTX n_(PUCCH) (2) 0, 0 19 NACK/DTX,NACK/DTX, NACK/DTX, ACK n_(PUCCH) (3) 1, 0 20 DTX, DTX, DTX, N/A N/A

Table 7 illustrates the HARQ-ACK mapping when all available resourcesare used (PUCCH resources and QPSK constellation points) and onlyHARQ-ACK states having an ACK value as the last value are mapped to thelast PUCCH resource (n_(PUCCH)(M−1)=n_(PUCCH)(3)).

TABLE 7 HARQ-ACK Multiplexing for 4 Node B PDSCH Transmissions—OnlyHARQ-ACK states with HARQ-ACK(3) = ACK are mapped on n_(PUCCH)(3) EntryHARQ-ACK(0), HARQ-ACK(1), HARQ- Number ACK(2), HARQ-ACK(3) n_(PUCCH)QPSK 1 ACK, ACK, ACK, ACK n_(PUCCH) (3) 1, 1 2 ACK, ACK, ACK, NACK/DTXn_(PUCCH) (2) 1, 1 3 NACK/DTX, NACK/DTX, NACK, DTX n_(PUCCH) (2) 0, 1 4ACK, ACK, NACK/DTX, ACK n_(PUCCH) (3) 0, 0 5 NACK, DTX, DTX, DTXn_(PUCCH) (0) 1, 0 6 ACK, ACK, NACK/DTX, NACK/DTX n_(PUCCH) (1) 1, 1 7ACK, NACK/DTX, ACK, ACK n_(PUCCH) (3) 0, 1 8 NACK/DTX, NACK/DTX,n_(PUCCH) (0) 1, 0 NACK/DTX, NACK 9 ACK, NACK/DTX, ACK, NACK/DTXn_(PUCCH) (0) 1, 1 10 ACK, NACK/DTX, NACK/DTX, ACK n_(PUCCH) (0) 0, 0 11ACK, NACK/DTX, NACK/DTX, n_(PUCCH) (0) 0, 1 NACK/DTX 12 NACK/DTX, ACK,ACK, ACK n_(PUCCH) (3) 0, 1 13 NACK/DTX, NACK, DTX, DTX n_(PUCCH) (1) 1,0 14 NACK/DTX, ACK, ACK, NACK/DTX n_(PUCCH) (2) 1, 0 15 NACK/DTX, ACK,NACK/DTX, ACK n_(PUCCH) (1) 0, 1 16 NACK/DTX, ACK, NACK/DTX, n_(PUCCH)(1) 0, 0 NACK/DTX 17 NACK/DTX, NACK/DTX, ACK, ACK n_(PUCCH) (3) 0, 1 18NACK/DTX, NACK/DTX, ACK, n_(PUCCH) (2) 0, 0 NACK/DTX 19 NACK/DTX,NACK/DTX, n_(PUCCH) (3) 1, 0 NACK/DTX, ACK 20 DTX, DTX, DTX, DTX N/A N/A

Table 8 illustrates the HARQ-ACK mapping when all available resourcesare used (PUCCH resources and QPSK constellation points) and allHARQ-ACK states having an ACK value as the last value are mapped to thelast PUCCH resource (n_(PUCCH)(M−1)=n_(PUCCH)(3)). In the example ofTable 8, the overlapped HARQ-ACK states are selected so that only theoutcome of the third PDSCH transmission is ambiguous. However, allcombinations leading to one of the first 3 PDSCH transmissions beingambiguous (regarding whether the PDSCH reception is correct) arepossible.

TABLE 8 HARQ-ACK Multiplexing for 4 Node B PDSCH Transmissions—AllHARQ-ACK states with HARQ-ACK(3) = ACK are mapped on n_(PUCCH)(3) EntryHARQ-ACK(0), HARQ-ACK(1), HARQ- Number ACK(2), HARQ-ACK(3) n_(PUCCH)QPSK 1 ACK, ACK, ACK, ACK n_(PUCCH) (3) 1, 1 2 ACK, ACK, ACK, NACK/DTXn_(PUCCH) (2) 1, 1 3 NACK/DTX, NACK/DTX, NACK, DTX n_(PUCCH) (2) 0, 1 4ACK, ACK, NACK/DTX, ACK n_(PUCCH) (3) 1, 1 5 NACK, DTX, DTX, DTXn_(PUCCH) (0) 1, 0 6 ACK, ACK, NACK/DTX, NACK/DTX n_(PUCCH) (1) 1, 1 7ACK, NACK/DTX, ACK, ACK n_(PUCCH) (3) 0, 1 8 NACK/DTX, NACK/DTX,n_(PUCCH) (0) 1, 0 NACK/DTX, NACK 9 ACK, NACK/DTX, ACK, NACK/DTXn_(PUCCH) (0) 1, 1 10 ACK, NACK/DTX, NACK/DTX, ACK n_(PUCCH) (3) 0, 1 11ACK, NACK/DTX, NACK/DTX, n_(PUCCH) (0) 0, 1 NACK/DTX 12 NACK/DTX, ACK,ACK, ACK n_(PUCCH) (3) 0, 0 13 NACK/DTX, NACK, DTX, DTX n_(PUCCH) (1) 1,0 14 NACK/DTX, ACK, ACK, NACK/DTX n_(PUCCH) (2) 1, 0 15 NACK/DTX, ACK,NACK/DTX, ACK n_(PUCCH) (3) 0, 0 16 NACK/DTX, ACK, NACK/DTX, n_(PUCCH)(1) 0, 0 NACK/DTX 17 NACK/DTX, NACK/DTX, ACK, ACK n_(PUCCH) (3) 1, 0 18NACK/DTX, NACK/DTX, n_(PUCCH) (2) 0, 0 ACK, NACK/DTX 19 NACK/DTX,NACK/DTX, n_(PUCCH) (3) 1, 0 NACK/DTX, ACK 20 DTX, DTX, DTX, DTX N/A N/A

Another embodiment of the present invention considers the reduction(including complete avoidance) of the number of HARQ-ACK states mappedto the same PUCCH resource and the same QPSK constellation point(overlapping HARQ-ACK states). To accomplish this objective, theinvention considers that the UE can assume that the DCI formatcorresponding to the PUCCH resource having overlapping HARQ-ACK statesconsists of at least 2 CCEs (or, in general, of a number of CCEs that isat least equal to the number of overlapping HARQ-ACK states). In thefollowing embodiment, the PUCCH resource notation is extended to alsoinclude the CCE index n of the respective DCI format and it can bedenoted as n_(PUCCH)(j,n), with n=0, . . . , N(j)−1, where N(j) is thetotal number of CCEs for DCI format j, with j=0, . . . , M−1.

The embodiment considers that HARQ-ACK signal transmission in a singleUL sub-frame corresponds to PDSCH transmissions in M=4 DL sub-frames(TDD system). Further, it is assumed by the mapping in Table 8 that thelast (fourth) DCI format consists of at least 2 CCEs. Table 9illustrates the transmission of the (overlapping in Table 8) HARQ-ACKstates when the DCI format for the PDSCH transmission in the last(fourth) DL sub-frame is assumed to consist of N(3)=2 CCEs. As can beseen, overlapping of HARQ-ACK states is avoided by separating thetransmission of the first and second overlapping HARQ-ACK states inTable 8 using n_(PUCCH)(3,0) and n_(PUCCH)(3,1), respectively. The NodeB receiver may determine the HARQ-ACK state transmitted by the UE byexamining the received signal energy at the candidate PUCCH resources aspreviously described.

TABLE 9 Transmission of Different HARQ-ACK for Overlapping Avoidance.PUCCH resource n_(PUCCH)(3, 0) PUCCH resource n_(PUCCH)(3, 1)HARQ-ACK(0), HARQ- HARQ-ACK(0), HARQ- Entry ACK(1), HARQ-ACK(2), ACK(1),HARQ-ACK(2), Number HARQ-ACK(3) HARQ-ACK(3) QPSK 1 ACK, ACK, ACK, ACK,ACK, NACK/DTX, 1, 1 ACK ACK 2 ACK, NACK/DTX, ACK, ACK, NACK/DTX, 0, 1ACK NACK/DTX, ACK 3 NACK/DTX, ACK, ACK, NACK/DTX, ACK, 0, 0 ACKNACK/DTX, ACK 4 NACK/DTX, NACK/DTX, NACK/DTX, 1, 0 NACK/DTX, ACK, ACKNACK/DTX, ACK

In the case of multiple UE transmitter antennas, TxD may selectivelyapply depending on whether overlapping HARQ-ACK states exist at thecorresponding PUCCH resource. For example, since all overlappingHARQ-ACK states in Table 8 occur in the PUCCH resource associated withthe last DCI format, ORTD may apply if the HARQ-ACK signal transmissionis in any PUCCH resource associated with the first 3 DCI formats.Conversely, if the HARQ-ACK signal transmission is in a PUCCH resourceassociated with the last (fourth) DCI format, both UE antennas transmitin the same PUCCH resource determined by the HARQ-ACK state, asdescribed, for example, in Table 9, in order to avoid the existence ofoverlapping HARQ-ACK states. Nevertheless, TxD may still apply in casethe HARQ-ACK signal transmission is in a PUCCH resource associated withthe last (fourth) DCI format by having one transmitter antenna transmitin the resource selected, as in Table 9, and have the second antennatransmit in a PUCCH resource associated with a DCI format in a differentDL sub-frame (or DL cell in the case of FDD).

FIG. 11 illustrates the application of ORTD for 2 UE transmitterantennas when the HARQ-ACK signal transmission is in a single ULsub-frame for M=4 DL sub-frames and the DCI format scheduling PDSCHtransmission in the DL last sub-frame can be assumed to be transmittedusing 2 CCEs. If the UE receives a DCI format in the last (fourth)sub-frame, that DCI format is assumed to include at least 2 CCEs. If theHARQ-ACK signal transmission is in PUCCH resources associated with a DCIformat in any of the first 3 DL sub-frames 1102, TxD applies (eitherwith conventional ORTD as in FIG. 8 or with the ORTD method described bythe first object of the invention in FIG. 9). If the HARQ-ACK signaltransmission is in PUCCH resources associated with a DCI format in thelast (fourth) DL sub-frame 1104, then both UE transmitter antennas 1110transmit in the same PUCCH resource. In n_(PUCCH)(3, 0), the mapping ofHARQ-ACK states to QPSK constellation points is: {NACK/DTX, ACK, ACK,ACK}→{0, 0} 1122, {ACK, NACK/DTX, ACK, ACK}→{0, 1} 1124, {ACK, ACK, ACK,ACK}→{1, 1} 1126, and {NACK/DTX, NACK/DTX, ACK, ACK}→{1, 0} 1128. Inn_(PUCCH)(3,1), the mapping of HARQ-ACK states to QPSK constellationpoints is: {NACK/DTX, ACK, NACK/DTX, ACK}→{0, 0} 1132, {ACK, NACK/DTX,NACK/DTX, ACK}→{0, 1} 1134, {ACK, ACK, NACK/DTX, ACK}→{1, 1} 1136, and{NACK/DTX, NACK/DTX, NACK/DTX, ACK}→{1, 0} 1138.

Another embodiment of the invention considers the mapping of HARQ-ACKstates to support HARQ-ACK multiplexing with carrier aggregation in FDDin the case of 2 DL cells. If the PDSCH Transmission Mode (TM) in eachcell requires the UE to convey 2 HARQ-ACK states for each PDSCHreception for a total of 4 HARQ-ACK states, the DCI format schedulingPDSCH reception with 2 TBs is assumed to require at least 2 CCEs for itstransmission with the first 2 CCEs providing 2 PUCCH resources for themapping of HARQ-ACK states for the HARQ-ACK signal transmission.Therefore, the DCI format in the first cell is associated with PUCCHresources n_(PUCCH)(0) and n_(PUCCH)(1) while the DCI format in thesecond cell is associated with PUCCH resources n_(PUCCH)(2) andn_(PUCCH)(3). Another consequence of always assuming at least 2 CCEs totransmit the DCI format scheduling PDSCH reception with 2 TBs is that,in the case of a single cell, it is always possible to support TxD usingthe 2 different PUCCH resources corresponding to the first 2 CCEs of theDCI format.

In general, several HARQ-ACK states used for HARQ-ACK multiplexing inTDD, as for example in Table 4 or Table 7, are not applicable for FDD(in the case of 2 cells and a TM for the PDSCH conveying 2 TBs) as DTXis applicable either to both of the first 2 or last 2 entries or none ofthem. This reduces the number of overlapping HARQ-ACK states andeliminates entries 3 and 5 of Table 4 or Table 7. Then, by combiningentries 8 and 13 in Table 4 or Table 7 into entry 13, the mapping inTable 7 is modified, as in Table 10. It is observed that the onlyoverlap is for entry 10 where DTX for one PDSCH is combined with {NACK,NACK} for the other PDSCH. Then, the only penalty is that one of theHARQ retransmissions is with the incorrect redundancy version. Such anevent has little to no impact on system throughput. Moreover, there isno overlapping if DTX feedback is not supported. Therefore, HARQ-ACKmultiplexing with 4 bits in the case of CA with 2 DL cells canpractically avoid all shortcomings of the one for TDD in Rel-8 (Table4). A candidate respective mapping is presented in Table 10.

TABLE 10 Mapping for HARQ-ACK Multiplexing with 4 States for FDD CA with2 DL Cells. Entry HARQ-ACK(0), HARQ-ACK(1), Number HARQ-ACK(2),HARQ-ACK(3) n_(PUCCH) QPSK 1 ACK, ACK, ACK, ACK n_(PUCCH) (3) 1, 1 2ACK, ACK, ACK, NACK n_(PUCCH) (2) 1, 1 3 ACK, ACK, NACK, ACK n_(PUCCH)(3) 0, 0 4 ACK, ACK, NACK/DTX, NACK/DTX n_(PUCCH) (1) 1, 1 5 ACK, NACK,ACK, ACK n_(PUCCH) (3) 0, 1 6 ACK, NACK, ACK, NACK n_(PUCCH) (0) 1, 1 7ACK, NACK, NACK, ACK n_(PUCCH) (0) 0, 0 8 ACK, NACK, NACK/DTX, NACK/DTXn_(PUCCH) (0) 0, 1 9 NACK, ACK, ACK, ACK n_(PUCCH) (2) 0, 1 10 NACK/DTX,NACK/DTX, n_(PUCCH) (1) 1, 0 NACK/DTX, NACK/DTX 11 NACK, ACK, ACK, NACKn_(PUCCH) (2) 1, 0 12 NACK, ACK, NACK, ACK n_(PUCCH) (1) 0, 1 13 NACK,ACK, NACK/DTX, NACK/DTX n_(PUCCH) (1) 0, 0 14 NACK/DTX, NACK/DTX, ACK,ACK n_(PUCCH) (0) 1, 0 15 NACK/DTX, NACK/DTX, ACK, NACK n_(PUCCH) (2) 0,0 16 NACK/DTX, NACK/DTX, NACK, ACK n_(PUCCH) (3) 1, 0 17 DTX, DTX, DTX,DTX N/A N/A

When the TM of the PDSCH in the first cell requires feedback from the UEof 2 HARQ-ACK states (for 2 TBs) and the TM of the PDSCH in the secondcell requires feedback from the UE of 1 HARQ-ACK state (for 1 TB), therespective mapping for HARQ-ACK multiplexing with 3 states can be as inTable 11.A. The DTX state for the PDSCH in the second cell is explicitlyindicated and mapped to PUCCH resource n_(PUCCH)(0) or n_(PUCCH)(1),both of which are associated with the DCI format transmission schedulingPDSCH reception in the first cell. The NACK state for the PDSCH in thesecond cell can be mapped to any PUCCH resource, such as, for example,n_(PUCCH)(2), which is associated with the DCI format transmissionscheduling PDSCH reception in the second cell. The ACK state for thePDSCH in the second cell can also be mapped to any resource, such as,for example, n_(PUCCH)(1). The exact QPSK constellation point is notrelevant to the proposed mapping.

TABLE 11.A Mapping for HARQ-ACK Multiplexing with 3 States. First 2States Correspond to Same PDSCH. Entry HARQ-ACK(0), HARQ-ACK(1), NumberHARQ-ACK(2) n_(PUCCH) QPSK 1 ACK, ACK, NACK n_(PUCCH) (2) 0, 0 2 ACK,NACK, NACK n_(PUCCH) (2) 0, 1 3 NACK, ACK, NACK n_(PUCCH) (2) 1, 0 4NACK, NACK, NACK n_(PUCCH) (2) 1, 1 5 ACK, ACK, ACK n_(PUCCH) (1) 0, 0 6NACK, ACK, ACK n_(PUCCH) (1) 0, 1 7 ACK, NACK, ACK n_(PUCCH) (1) 1, 0 8NACK, NACK, ACK n_(PUCCH) (1) 1, 1 9 ACK, ACK, DTX n_(PUCCH) (0) 0, 0 10ACK, NACK, DTX n_(PUCCH) (0) 0, 1 11 NACK, ACK, DTX n_(PUCCH) (0) 1, 012 NACK, NACK, DTX n_(PUCCH) (0) 1, 1 13 DTX, DTX, DTX N/A N/A

The same principles apply in the case in which the TM of the PDSCH inthe second cell requires feedback from the UE of 2 HARQ-ACK states (for2 TB s) and the TM of the PDSCH in the first cell requires feedback fromthe UE of 1 HARQ-ACK state (for 1 TB). The respective mapping forHARQ-ACK multiplexing with 3 states is then obtained by simply switchingthe first and third HARQ-ACK states in Table 11.A as shown in Table11.B.

TABLE 11.B Mapping for HARQ-ACK Multiplexing with 3 States. Last 2States Correspond to Same PDSCH. Entry HARQ-ACK(0), HARQ-ACK(1), NumberHARQ-ACK(2) n_(PUCCH) QPSK 1 NACK, ACK, ACK n_(PUCCH) (2) 0, 0 2 NACK,NACK, ACK n_(PUCCH) (2) 0, 1 3 NACK, ACK, NACK n_(PUCCH) (2) 1, 0 4NACK, NACK, NACK n_(PUCCH) (2) 1, 1 5 ACK, ACK, ACK n_(PUCCH) (1) 0, 0 6ACK, ACK, NACK n_(PUCCH) (1) 0, 1 7 ACK, NACK, ACK n_(PUCCH) (1) 1, 0 8ACK, NACK, NACK n_(PUCCH) (1) 1, 1 9 DTX, ACK, ACK n_(PUCCH) (0) 0, 0 10DTX, ACK, NACK n_(PUCCH) (0) 0, 1 11 DTX, NACK, ACK n_(PUCCH) (0) 1, 012 DTX, NACK, NACK n_(PUCCH) (0) 1, 1 13 DTX, DTX, DTX N/A N/A

In the case in which the TM of the PDSCH in either of the 2 cellsrequires feedback from the UE of 1 HARQ-ACK state (for 1 TB), therespective mapping for HARQ-ACK multiplexing with 2 states can be as inTable 12. The DTX state for either cell is explicitly mapped. PUCCHresource n_(PUCCH)(1), corresponding to the first CCE of the DCI formatscheduling the PDSCH reception in the second cell, is used to map theDTX state for the first cell while PUCCH resource n_(PUCCH)(0),corresponding to the first CCE of the DCI format scheduling the PDSCHreception in the first cell, is used to map the DTX state for the secondcell. The NACK or ACK state can be mapped to any PUCCH resource. Theexact point of the QPSK constellation is, again, not relevant to theproposed mapping.

TABLE 12 Mapping for HARQ-ACK Multiplexing with 2 States for FDD CA with2 Cells. HARQ-ACK(0), HARQ- ACK(1) n_(PUCCH) QPSK ACK, NACK n_(PUCCH)(1) 0, 0 NACK, NACK n_(PUCCH) (1) 0, 1 DTX, NACK n_(PUCCH) (1) 1, 0 DTX,ACK n_(PUCCH) (1) 1, 1 ACK, ACK n_(PUCCH) (0) 0, 0 NACK, ACK n_(PUCCH)(0) 0, 1 ACK, DTX n_(PUCCH) (0) 1, 0 NACK, DTX n_(PUCCH) (0) 1, 1 DTX,DTX N/A N/A

The UE operation for HARQ-ACK signal transmission with multiplexing inan FDD system where the UE receives PDSCH in two DL cells is describedin FIG. 12. If the TM for the PDSCH in first cell conveys 1 TB and theTM for the PDSCH in the second cell conveys 1 TB 1210, then the UE usesthe mapping of HARQ-ACK states in Table 12 1220. Otherwise, if the TMfor the PDSCH in first cell conveys 2 TBs and the TM for the PDSCH inthe second cell conveys 2 TBs 1230, then the UE uses the mapping ofHARQ-ACK states in Table 10 1240. Otherwise, if the TM for the PDSCH infirst cell conveys 2 TBs and the TM for the PDSCH in the second cellconveys 1 TB 1250, then the UE uses the mapping of HARQ-ACK states inTable 11.A 1260. Otherwise, the UE uses the mapping of HARQ-ACK statesin Table 11.B 1270.

While the present invention has been shown and described with referenceto certain embodiments thereof, it will be understood by those skilledin the art that various changes in form and details may be made thereinwithout departing from the spirit and scope of the present invention asdefined by the appended claims.

What is claimed is:
 1. A method for transmitting a hybrid automaticrepeat request-acknowledgement (HARQ-ACK) signal in a communicationsystem, the method comprising: receiving at least one transport block ona physical downlink shared channel (PDSCH) indicated by a physicaldownlink control channel (PDCCH) on a cell; and transmitting at leastone HARQ-ACK signal for the at least one transport block on a first andsecond physical uplink control channel (PUCCH) resource, wherein thePDCCH comprises at least one control channel element (CCE), and whereinthe first PUCCH resource is identified based on a first CCE used fortransmission of the PDCCH, and for a transmission mode that supports upto two transport blocks, and the second PUCCH resource is identifiedbased on the first CCE+1.
 2. The method of claim 1, further comprising:receiving at least one transport block on a PDSCH indicated by a PDCCHon another cell.
 3. The method of claim 1, wherein the cell is a firstcell.
 4. The method of claim 2, further comprising: identifying a thirdPUCCH resource and a fourth PUCCH resource for the another cell.
 5. Themethod of claim 1, wherein a HARQ-ACK state for the at least oneHARQ-ACK signal for the at least one transport block is mapped to one ofthe first and second PUCCH resource.
 6. A method for receiving a hybridautomatic repeat request-acknowledgement (HARQ-ACK) signal in acommunication system, the method comprising: transmitting at least onetransport block on a physical downlink shared channel (PDSCH) indicatedby a physical downlink control channel (PDCCH) on a cell; and receivingat least one HARQ-ACK signal for the at least one transport block on afirst and second physical uplink control channel (PUCCH) resource,wherein the PDCCH comprises at least one control channel element (CCE),and wherein the first PUCCH resource is identified based on a first CCEused for transmission of the PDCCH, and for a transmission mode thatsupports up to two transport blocks, and the second PUCCH resource isidentified based on the first CCE+1.
 7. The method of claim 6, furthercomprising: transmitting at least one transport block on a PDSCHindicated by a PDCCH in another cell.
 8. The method of claim 6, whereinthe cell is a first cell.
 9. The method of claim 6, wherein a HARQ-ACKstate for the at least one HARQ-ACK signal for the at least onetransport block is mapped to one of the first and second PUCCHresources.
 10. An apparatus for transmitting a hybrid automatic repeatrequest-acknowledgement (HARQ-ACK) signal in a communication system, theapparatus comprising: a receiver configured to receive at least onetransport block on a physical downlink shared channel (PDSCH) indicatedby a physical downlink control channel (PDCCH) on a cell; and atransmitter configured to transmit at least one HARQ-ACK signal for theat least one transport block on a first and second physical uplinkcontrol channel (PUCCH) resource, wherein the PDCCH comprises at leastone Control Channel Element (CCE), and wherein the first PUCCH resourceis identified based on a first CCE used for transmission of the PDCCH,and for a transmission mode that supports up to two transport blocks,and the second PUCCH resource is identified based on the first CCE+1.11. The apparatus of claim 10, wherein the receiver receives at leastone transport block on a PDSCH indicated by a PDCCH in another cell. 12.The apparatus of claim 10, wherein the cell a first cell.
 13. Theapparatus of claim 11, further comprising: a processor configured toidentify a third PUCCH resource and a fourth PUCCH resource for theanother cell.
 14. The apparatus of claim 10, wherein a HARQ-ACK statefor the at least one HARQ- ACK signal for the at least one transportblock is mapped to one of the first and second PUCCH resources.
 15. Anapparatus for receiving a hybrid automatic repeatrequest-acknowledgement (HARQ-ACK) signal in a communication system, theapparatus comprising: a transmitter configured to transmit at least onetransport block on a physical downlink shared channel (PDSCH) indicatedby a physical downlink control channel (PDCCH) on a cell; and a receiverconfigured to receive at least one HARQ-ACK signal for the at least onetransport block on a first and second physical uplink control channel(PUCCH) resource, wherein the PDCCH comprises at least one controlchannel element (CCE), and wherein the first PUCCH resource isidentified based on a first CCE used for transmission of the PDCCH, andfor a transmission mode that supports up to two transport blocks, andthe second PUCCH resource is identified based on the first CCE+1. 16.The apparatus of claim 15, wherein the transmitter transmits at leastone transport block on a PDSCH indicated by a PDCCH in another cell. 17.The apparatus of claim 15, wherein the cell is a first cell.
 18. Theapparatus of claim 15, wherein a HARQ-ACK state for the at least oneHARQ-ACK signal for the at least one transport block is mapped to one ofthe first and second PUCCH resources.